A Numerical Smith Diagram Revision for Modern Low Pressure Turbine Profiles

Smith diagram is historically one of the standard tools used for turbine design, especially in concept design phase (CD) and for assessment/comparison of turbine configurations. For each turbomachinery stage, this graph provides a relation among stage loading factor (y), flow coefficient (f) and aerodynamic performance (). However, various essential inputs such as stage reactions (R), aspect ratios (AR) or Reynolds numbers (Re), or outputs like flow deflections (d), profile weights and stresses are not directly taken into account. In the work here presented, traditional loss correlation models (Craig & Cox (C&C) and Ainley & Mathieson, Dunham & Came, Kacker & Okapuu (AMDCKO)), are used to evaluate stage performance and then to derive a more complete vision of key parameters. Starting from a representative turbine configuration, once some main characteristic boundary conditions (BC) have been defined, few parameters are changed in order to obtain a stage operating in a specific region of the Smith diagram. By this way, it has been possible to compare experimental data from original Smith with computational results obtained with such approach. Moreover, additional details previously missing (both aerodynamic and mechanical) have been obtained and optimal design considerations have been investigated under a multidisciplinary point of view. In addiction, by means of dedicated tools, blade geometries have been prepared for some of these configurations. Some preliminary CFD 3D analyses have then been run to improve specific understandings. This research leads to extend Smith diagram with many other important information for turbine module design and to numerically revise the diagram itself, adjusting it with data coming from modern high performance profile’s analyses.